The design and performance of golf clubs is greatly influenced by the choice of materials from which they are fabricated. It has been recognized that bulk-solidifying amorphous metals (i.e., metallic glasses) as a class of materials possess certain inherent attributes such as high strength and hardness, high elastic strain limit, and material density varying over a useful range, that make them highly attractive for use various golf clubs including drivers, fairway woods, irons, and putters. Specifically, Scruggs et al. (U.S. Pat. No. 6,685,577) and Johnson et al. (U.S. Pat. No. 7,357,731) have described the benefits arising from these inherent properties of bulk-solidifying amorphous metals in the design and performance of such golf clubs. For example, both Scruggs et al. and Johnson et al. claimed in these patents that the high elastic strain limit of metallic glasses can be potentially exploited to design a golf driver with an exceptionally high coefficient of energy restitution, thereby enabling the golfer to achieve greater distance on a drive. It was also conjectured that the high strength of metallic glass would permit the design of golf irons in which the mass of the club can be concentrated to a greater extent on the perimeter of the iron. It was thought that such design freedom would allow for a club that was more resistant to the “hooking” or “slicing” that occurs when a ball is struck off the “sweet spot” of the club.
In practice, the actual use of metallic glasses in golf clubs has been limited and constrained by other key material properties of available metallic glass materials. Examples of other important properties include elastic stiffness (Young's Modulus}, fracture toughness (notch toughness), ductility under bending, endurance under cyclic loading (fatigue behavior), and general tendency toward brittle catastrophic failure. These properties were not considered as relevant to the design of golf clubs in the prior art, however, the lack of low cost metallic glasses with appropriate combinations of high elastic strain limit, high strength, and density in a useful range together with adequately high values for the aforementioned additional properties has limited the wide-spread adoption of metallic glasses in the golf industry by club designers and engineers. Specifically, the use of metallic glasses in commercial golf clubs has been constrained by the absence of low cost, processable metallic glasses with high modulus, high fracture toughness, high fatigue endurance, adequate bend ductility, and material density in a useful range.